Projected sea level rise, gyre circulation and water mass formation in the western North Pacific: CMIP5 inter-model analysis

Abstract

Future changes in the dynamic sea level (DSL), which is defined as sea-level deviation from the global mean sea level, is investigated over the North Pacific, by analyzing data from the Coupled Model Intercomparison Project Phase 5. The analysis provides more comprehensive descriptions of DSL responses to the global warming in this region than available from previous studies, by using surface and subsurface data until the year 2300 under middle and high greenhouse-gas emission scenarios. The DSL changes in the North Pacific are characterized by a DSL rise in the western North Pacific around the Kuroshio Extension (KE), as also reported by previous studies. Subsurface density analysis indicates that DSL rise around the KE is associated with decrease in density of subtropical mode water (STMW) and with northward KE migration, the former (latter) of which is relatively strong between 2000 and 2100 for both RCP4.5 and RCP8.5 (between 2100 and 2300 for RCP8.5). The STMW density decrease is related to large heat uptake to the south and southeast of Japan, while the northward KE migration is associated with the poleward shift of the wind stress field. These features are commonly found in multi-model ensemble means and the relations among representative quantities produced by different climate models.

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Acknowledgements

We thank Dr. Tatsuo Suzuki, Dr. Tamaki Yasuda, and Dr. Yoshi N. Sasaki for fruitful discussions. We also thank Dr. Tamaki Yasuda for providing some of the CMIP5 data used in this study. We acknowledge the climate modeling groups and the World Climate Research Programme’s Working Group on Coupled Modelling for producing and making their model output available, and the US Department of Energy and other agencies contributing Easrth System Grid Federation for their roles in collecting and archiving the model output. This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant numbers 26287110, 26610146, and 15H01606.